Westerly winds were actively forming new wind slabs over the day on Thursday. Raise your guard as you reach upper treeline and alpine elevations.
Wind transport was ongoing on Thursday, likely leaving new wind slabs perched in leeward terrain features. These could be reactive to human triggering on Friday. Alpine is the primary concern but specific upper treeline features may hold small new slabs as well.
A deep weak layer affecting alpine areas could result in very large, destructive avalanches. Wind slab releases have potential to trigger this layer to produce even larger avalanches.
Thursday night: Clear. Light to moderate west winds, easing.
Friday: Sunny, clouding over in the evening. Light variable winds. Treeline high temperatures around -8.
Saturday: Mainly cloudy with isolated flurries continuing from the overnight period, mainly in the south of the region. Light west winds. Treeline high temperatures around -9.
Sunday: Mainly sunny. Light northwest winds. Treeline high temperatures around -10.
Although details are still limited, a natural storm slab avalanche cycle occurred over Tuesday night. A new report from Hurley Pass Thursday morning details a widespread natural avalanche cycle yielding releases to size 3.5 (very large). Similar conditions were very likely in many areas of the region on Tuesday night and sizes suggest that some avalanches involved persistent layers discussed in our snowpack summary.
A report from explosives control in the Duffey Lake area Wednesday showed debris from releases up to size 2 (large) reaching quite low in tracks and runouts, aided by old debris from the last storm's avalanche cycle.
Looking forward, alpine areas remain a concern both for the presence of new wind slabs and for the possibility of persistent slabs remaining reactive to human triggers. Cooling temperatures will aid in stabilizing the snowpack, especially at lower elevations, but the alpine may need more time to adjust to the significant load of new snow.
Moderate to strong westerly winds were observed forming new wind slabs on the surface from upper treeline to alpine in the neighbouring Sea to Sky on Thursday. Similar action was likely taking place farther inland.
The warm, wet storm from early in the week brought 20-30 mm of precipitation to the region. Above an estimated 2100 metres, this fell as snow under the influence of strong southwest winds. This added to the load over a layer of surface hoar now down an estimated 90-120 cm as well as a deeper crust/facet combo layer that produced large avalanches during the region's last storm (Saturday).
Rain-wetted surfaces below about 2100 m have undergone a refreeze that should effectively lock the snowpack in place at lower elevations.
Average snowpack depths in the alpine are now likely closer to 150-200 cm. Below treeline, depths of 30-50 cm have been reported around 500 m, decreasing dramatically with elevation, and still below threshold for avalanches in many areas. Early season hazards such as rocks, stumps, and creeks are still a concern below the alpine.
